[spandeli]

Originally Posted by doughboy

Tony -

What about fitting the M3 ARB's and their more rigid mounts? Are they compatible?

M3 front = 26.5mm
M3 rear = 20mm

I notice BMW have different part number for ARBs with the same diameter??? on E90/E91 regular models. They show the same between some models, indicating the same bar will fit both models. Then for m sport variants of the said models, they have same diameter ARBs with different part numbers...

Is this due to different geometries or materials? thus meaning the diameter itself is useless as an indicator between models?

What i know for sure from my personal experience is that the front ARB of the M Sport is different than the one fitted in the SE models.

[Hoops]

Didn't realise Hartge supplied ARB's for the Laguna - nice!!

[E92Fan]

Originally Posted by doughboy

Tony -

What about fitting the M3 ARB's and their more rigid mounts? Are they compatible?

M3 front = 26.5mm
M3 rear = 20mm

I notice BMW have different part number for ARBs with the same diameter??? on E90/E91 regular models. They show the same between some models, indicating the same bar will fit both models. Then for m sport variants of the said models, they have same diameter ARBs with different part numbers...

Is this due to different geometries or materials? thus meaning the diameter itself is useless as an indicator between models?

You can fit the M3 ARBs front & rear directly - there are no additional modifications needed. What you will find is that the roll stiffness is increased, so obviously you get less body roll, whilst at the same time the handling balance of the car remains balanced front and rear. The M3 bars still give a tendancy to understeer at the limit, which is how BMW have designed their cars to give an element of safety. Certainly you don't want a setup that will induce snap oversteer!

Whilst the diameter of the bars between SE and MSports are the same, the part numbers are different because the MSport ARBs are designed slightly differently to be compatible with the lower MSport suspension.

In general, the diameter of the bar is largely useless as a single means of calculating the stiffness of an antiroll bar - much of the torsional rigidity is down to material choice, thickness, stress points, and mounting design.

That's why simply choosing a 28mm bar from Hartge to match to a 20mm bar from Eibach, for instance, is a guaranteed recipe for disaster - those bars will have completely different designs and parameters, and you won't know which way the biasing has gone.

If you are going to upgrade the rollbars, you MUST use a matched pair - Eibach, Hartge or M3. For me, the M3 bars are still a bit on the soft side, and are still biased too much towards understeer. The roll resistance is of course much better than your standard setup, but it doesn't go far enough to provide the throttle adjustability that I have with the Hartge setup. I've driven a car with the Eibachs, but didn't spend enough time in the car to accurately gauge its responses. I think Spin and Acerboo both have Eibach ARBs, so they will be the people to answer that question.

As for me, of all the E9x I've driven, and even though I admit to a modicum of bias, the way my car handles is the almost perfect setup for me. I have complete throttle adjustability through constant radius corners - and I can still tell the onset of limit of grip, because the ARBs aren't so aggressive as to rob all feel from the handling.

[doughboy]

Thanks Tony -

Been speaking to Kevin Bird and I'm leaning toward the Hartge ARBs. (BTW Hartge supply indentical suspension upgrades for E90 and E91)

Do the Hartge ARBs come with poly mounting bushes or plain rubber?

Are they adjustable / multi hole i.e. obviousy not OEM?

many thanks..

[E92Fan]

Originally Posted by doughboy

Thanks Tony -

Been speaking to Kevin Bird and I'm leaning toward the Hartge ARBs. (BTW Hartge supply indentical suspension upgrades for E90 and E91)

Do the Hartge ARBs come with poly mounting bushes or plain rubber?

Are they adjustable / multi hole i.e. obviousy not OEM?

many thanks..

Ah ha... that makes sense now!! Was speaking to Kevin yesterday The Hartge bars are fantastic, regardless of my bias or lack thereof

They used to do an adjustable roll-bar set, but I'm not sure it was ever designed for the E9x series. I think the adjustables were only for the E46. Even if there were an adjustable set for the E9x, I wouldn't bother as the handling balance is nigh-on perfect with the normal Hartge ARBs.

From memory, the bushes are polybushes, or at the very least very heavy duty low-modulus rubber bushes... think they are poly though - can check for you tomorrow...

[Ant Man]

Fyi- Hartge do not make their anti-roll bars. They are made by H&R. I think the arb with Hartge stickers are a fair bit more expensive than the H&R but are identical.

Doughboy, check out prices before you buy. Teddy at SSDD-motorsport is good on price and service. Let him know I recommended him.

[E92Fan]

Originally Posted by Ant Man

Fyi- Hartge do not make their anti-roll bars. They are made by H&R. I think the arb with Hartge stickers are a fair bit more expensive than the H&R but are identical.

Doughboy, check out prices before you buy. Teddy at SSDD-motorsport is good on price and service. Let him know I recommended him.

I beg to differ - I have a set of H&Rs sitting in my storage unit, and they aren't the same as the Hartge bars. For a start, the H&R front bar is a 27mm diameter unit - the Hartge bar is 28mm. Also the drop linkages are of a different design. I don't know where you got your information from, but FACT - the H&R bars ARE NOT THE SAME as the Hartge bars... It is possible that Hartge outsourced manufacturing to H&R - it wouldn't surprise me as that would ensure the highest quality of product. But to say they're identical is very misleading and to say that the Hartge product just simply has a higher pricetag on (which it may or may not have) is not justified in this instance.

Oh, and before anyone accuses me of being a Hartge fanboy, I'm not... the Hartge suspension is way too stiff in the rear to be used as an everyday car, for instance, and the wheels are just way too large for the car...

[Ant Man]

fanboy - that's an expression I haven't heard for a while

I stand corrected on the appearance but I understand that the performance as measured is near identical.

[SiKkBaSs]

Originally Posted by zltm089

Another good review!!! Tony strikes again!

/Thread

Good work Tone

[E92Fan]

Originally Posted by Ant Man

fanboy - that's an expression I haven't heard for a while

I stand corrected on the appearance but I understand that the performance as measured is near identical.

Technically I think I should have spelt it "fanboi"

You may well be right Antman in saying that the performance of the two setups is very similar. The thing is, the torsional rigidity of the anti-roll bars is not just determined by its diameter. Thickness of material, and design of bar play just an important part. For instance, having longer arms will have a different leverage force, therefore negatively changing the torsional rigidity...

Bearing this in mind then, it would be largely impossible to say how the two bar setups compare in technical performance without putting each one on a measurement rig.

What is most important is the relationship between the front and rear bars - that is the factor that most determines the handling balance between front and rear (in terms of oversteer, understeer, or neturality). Of course, the relative strengths of each bar will also determine the roll-resistance, but given that the H&Rs and Hartges each run either 27/28mm and 20mm bars, you can take it for granted that roll resistance is greatly reduced over the standard 13mm bar BMW specify



Have a ponder over this though - an anti-roll bar resists torsion forces through its stiffness. The stiffness of an anti-roll bar is based on the fourth power of its diameter, the stiffness of the material, the inverse of the length of the lever arms (ie. the shorter the lever arm, the stiffer the bar), the geometry of the mounting points, and the rigidity of the bar's mounting points.

Compare the diameters of a 27mm H&R front bar, and a 28mm Hartge front bar...


In terms of the stiffness derived from it's diameter -

the fourth power of 27 is 531,441
the fourth power of 28 is 614,656

You can see that just by going from a 27mm to a 28mm diameter bar, all other things being equal, there is an increase in stiffness derived from diameter of 15.66%.



So, whilst I don't dispute that the relative performances of the H&R and Hartge anti-roll bars might be quite similar, I would struggle to say that they are identical, as the difference in design and bar diameters would be enough to create a quite significant difference in performance.

[Ant Man]

Are you assuming that both pairs of arb are made of the same material and are both either hollow or solid to make your comparison?

I know that many arb are hollow (M3 for instance) and as you say, only by physically measuring their stiffness on a jig will you know the stiffness of each and can make a comparison

There has been a huge amount of discussion on the US Supension forum on this subject and the numbers have all been posted. Harold from HP Autoworks and Orb are the experts.

[RagingKileak]

Hey Tony,

Do you think in conjunction with an LSD this is an appropriate mod for an intermediate driver?

Matt

[E92Fan]

Originally Posted by E92Fan

Technically I think I should have spelt it "fanboi"

You may well be right Antman in saying that the performance of the two setups is very similar. The thing is, the torsional rigidity of the anti-roll bars is not just determined by its diameter. Thickness of material, and design of bar play just an important part. For instance, having longer arms will have a different leverage force, therefore negatively changing the torsional rigidity...

Bearing this in mind then, it would be largely impossible to say how the two bar setups compare in technical performance without putting each one on a measurement rig.

What is most important is the relationship between the front and rear bars - that is the factor that most determines the handling balance between front and rear (in terms of oversteer, understeer, or neturality). Of course, the relative strengths of each bar will also determine the roll-resistance, but given that the H&Rs and Hartges each run either 27/28mm and 20mm bars, you can take it for granted that roll resistance is greatly reduced over the standard 13mm bar BMW specify



Have a ponder over this though - an anti-roll bar resists torsion forces through its stiffness. The stiffness of an anti-roll bar is based on the fourth power of its diameter, the stiffness of the material, the inverse of the length of the lever arms (ie. the shorter the lever arm, the stiffer the bar), the geometry of the mounting points, and the rigidity of the bar's mounting points.

Compare the diameters of a 27mm H&R front bar, and a 28mm Hartge front bar...


In terms of the stiffness derived from it's diameter -

the fourth power of 27 is 531,441
the fourth power of 28 is 614,656

You can see that just by going from a 27mm to a 28mm diameter bar, all other things being equal, there is an increase in stiffness derived from diameter of 15.66%.



So, whilst I don't dispute that the relative performances of the H&R and Hartge anti-roll bars might be quite similar, I would struggle to say that they are identical, as the difference in design and bar diameters would be enough to create a quite significant difference in performance.

Originally Posted by Ant Man

Are you assuming that both pairs of arb are made of the same material and are both either hollow or solid to make your comparison?

My comparison above is solely taking into account bar stiffness derived from the diameter. This is only ONE of several factors determining overall bar stiffness. Going from a 27mm to 28mm bar, all other aspects being equal, gives an increase in stiffness derived from diameter o 15.66%

Originally Posted by Ant Man

I know that many arb are hollow (M3 for instance) and as you say, only by physically measuring their stiffness on a jig will you know the stiffness of each and can make a comparison

That is correct - in determining the overall torsional rigidity of each bar, the only way to measure is on a jig. Comparing diameters alone is entirely irrelevant because that doesn't take into account any of the other aspects of bar design - length of droplinks, leverage of arms, material thickness, hollow or solid etc etc...


Orb and Harold have had many a discussion over on the US forum - however whilst they have posted 'numbers', largely their numbers are relative to what they have seen from design, and not based on actual empirical data taken off a force-measurement jig. At the end of the day, the only way to choose a good set of bars is to try and ascertain the relationship between front and rear torsional rigidity of each set. Some sets will be biased more towards front antiroll (and therefore more understeer) whilst others will have a more balanced setup (neutral cornering), and then there will be some which are rear-biased (leading to oversteer). What I don't understand is why people mix and match rollbars - for instance use an M3 front and Eibach rear, or some other weird combination. Surely that approach is completely down to potluck ??!!

[E92Fan]

Originally Posted by RagingKileak

Hey Tony,

Do you think in conjunction with an LSD this is an appropriate mod for an intermediate driver?

Matt

The question I'd pose in response is what are you looking to achieve from your car? If you are after better handling, in terms of cornering ability and precision, then yes the rollbars will give you a more feelsome drive through corners. By installing uprated rollbars, whether Eibach or Hartge or otherwise, you are reducing the amount of traction through the rear wheels and so an LSD is highly recommended to address that issue.

If you are simply looking for more traction, greater usability of the engine power, and more fun, then you can go down the LSD-only route, without the rollbars.

My personal view is that the LSD allows you to extract considerably more out of your car's capability - whether you are a novice, intermediate or advanced driver, this will be a noticeable difference. The more advanced you are, the more you will appreciate and benefit from the LSD. If you're not at that advanced level yet, then I am sure that one of your goals will be to improve the standard of driving to that advanced level.

So in a short answer, yes I think it's an appropriate mod, both the rollbars and the LSD. Getting both done at the same time saves labour on the rear end too!!

An even better mod after all that though would be to get yourself on to a course like the Driver Development Programme (www.driverdp.com), which will allow you to explore all the possibilties and capabilities of the car, develop your skills, and learn how to drive an LSD-equipped car properly! And I don't say that in a condescending way at all - I'm doing a refresher DPP course fairly soon as I haven't had the opportunity to practice certain skills out on public roads...!!

[RagingKileak]

I agree with the driver training.

I have done a couple of sort of tuition days and I am very keen to do one in my own car being very different from those I played in previously of course.

I believe I am more than capable of achieving good results from cars which allow more able drivers to push them further - the E46 M3 was a car which I could drive quite well, and I do notice the difference in my E90.

I did once push the M3 too far and I have to admit, it was a bit scarier than when I come close to pushing the E90 too far - whether this is because the E90 gives up easier because its less capable or as you have suggested before - because by the time the M3 gives up your already in a world of trouble.

I dont want to find that in my E90 I am suddenly always in a world of trouble ya know?

I guess thats what I am wondering... Will a remapped 335D with an LSD and an ARB kit, be more of a handful than an E46 M3 in the hands of a driver who is capable, but not world beating?

The M3 is undoubtedly quick, but I suspect due to the amount of donuts driving them they will have allowed some margins of safety...

The 335D with above mods could possibly eliminate those margins of safety, and on the one day I fuck up - am I going to end up smeared all over the pavement? Or rather, is whatever I hit going to end up with a 6 cylinder battering ram coming at them....

Ah what a load of bollox I have just written... still hopefully you get the gist...

Matt